Semiconductor memory devices such as DRAM memory devices can experience the dissipation of charges stored in a cell capacitor in the form of leakage current. Thus, a refresh operation of reading out data stored in a DRAM and then writing the data again periodically before the data completely disappears may be needed.
In the case that a computer is in a sleep mode, most internal devices are turned off but a DRAM is turned on for data retention. In this case, a DRAM performs a self refresh operation to retain data.
To further strengthen the low power consumption of a notebook, a smart phone, etc. that operates by a battery, a method of reducing power consumption in a DRAM may be useful.